1. Field of the Invention
The present invention relates generally to pressure transducers and pertains, more particularly, to pressure transducers for use with injection molding machines.
2. Discussion of Related Art
Injection molding machines are used to manufacture plastic and metal parts. Injection molding machines typically include a reservoir of molten plastic and a nozzle through which the molten plastic is forced at high pressures into a mold. The plastic is thereafter packed and cooled to form the part. In the manufacture of such parts, it is important to precisely determine the pressure of the injected melt to maintain accuracy of the part because the part must be made at a constant pressure. This is so because otherwise the resulting part may include voids, ripples, poor dimensional accuracy or the like.
As such, there is a need for pressure transducer devices which can accurately measure the pressure of molten plastic within injection molding machines. Attaining accuracy in pressure measurements by injection molding machine pressure transducers is difficult because pressures within such injection molding machines may be as high as within the range of 40-50,000 psi and the temperature may be as high as approximately 500.degree. C. In other words, such pressure transducers must be able to accurately measure and withstand pressures within the range of 40-50,000 psi and operate accurately within an environment having temperatures up to approximately 500.degree. C. Additionally, such pressure transducers are faced with the following constraints: 1. the pressure transducer must have low working stresses to avoid metal fatigue cracking under repetative cyclic loading; 2. the pressure transducer, for economic practicality, must be physically arranged such that it can easily be integrated within injection molding machines shot chamber/nozzle area; and 3. the pressure transducer must not disrupt the plastic flow or have pockets where plastic will remain and eventually degrade and cause staining of the parts as the degraded plastic moves into the flow.
Accordingly, a general object of the present invention is to provide an injection molding machine pressure transducer which can accurately measure pressures of molten plastic within such machines.
A further object of the present invention is to provide an injection molding machine pressure transducer which is easily integratable with existing injection molding machines.